<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
<style>
    div{
        width:200px;
        height: 200px;
        
    }
    .b1{
        background-color: red;
        border: 1px solid yellow;
        margin-bottom: 50px;
    }
    .b2{
        background-color: green;
        border: 1px solid blue;
    }
    /*margin-top/left/bottom/right*
    一个值 四个方向
    两个值 上下左右
    三个值 上 左右 下
    四个值 上右下左*/
    .c1{
        background-color: red;
       width: 500px;
       height: 500px;
       
    }
    .c2{
        background-color: yellow;
        margin-right: 50px;
        float:left
    }
    .c3{
        background-color: green;
       margin-left:50px ;
      float: left;  
    }
    .c4{
        
        background-color: yellow;
       margin: 100px;
       float: left;
    }
</style>
</head>
<body>
    <!-- <div class="b1"></div>
    <div class="b2"></div> -->

    <div class="c1">
        <div class="c4"></div>
    </div>
    
    <!-- <div class="c2"></div>
    <div class="c3"></div> -->
</body>
</html>